1. Field of the Disclosure
The disclosure relates to a fan, more particularly to a fan having a backflow prevention device.
2. Description of the Related Art
A network server is demanded to provide services uninterruptedly, and is equipped with a fan assembly for heat dissipation. The fan assembly draws cool air from an upstream side for dissipating heat from electronic components of the server, and exhausts heated air toward a downstream side. Once a fan of the fan assembly breaks down, the heated air disposed at the downstream side of the fan assembly may be drawn toward the electronic components (i.e., a backflow occurs) since an air pressure at the downstream side is greater than that at the upstream side, so that a cooling capacity of the fan assembly may thereby be lowered.
Referring to FIGS. 1 and 2, a conventional fan of such a fan assembly (not shown) includes a fan body 91 and a backflow prevention device 92. The fan body 91 includes a casing 911 that has an airflow inlet 9A and an airflow outlet 9B opposite to the airflow inlet 9A, a blade unit 912 that is disposed rotatably in the casing 911 and that is adjacent to the airflow inlet 9A, and a plurality of stator blades 913 that are formed integrally in the casing 911 and that is adjacent to the airflow outlet 9B. The backflow prevention device 92 includes a mounting frame 921 that is disposed adjacent to the airflow outlet 9B, and a plurality of slats 922 that are connected pivotally to the mounting frame 921 and that are parallel to each other.
When the blade unit 912 rotates to generate an airflow that enters the casing 911 via the airflow inlet 9A and exits the casing 911 via the airflow outlet 9B, the stator blades 913 serves to concentrate and intensify the airflow, and the slats 922 are opened for passage of the airflow (see FIG. 1).
When the blade unit 912 is stopped, the slats 922 are driven by a backflow resulting from a pressure difference between opposite sides of the backflow prevention device 92 to close the airflow outlet 9B of the casing 911 (see FIG. 2) for preventing further backflows.
However, the slats 922 may diminish the airflow that is generated by the blade unit 912 and intensified by the stator blades 913. Moreover, the conventional fan has a considerable thickness.